Reports

Report Number: 156
Year: 2015
 

Assessment of Turbidity in the Geus River Watershed in Southern Guam

In February 2014, the National Oceanic and Atmospheric Administration (NOAA) announced the designation of Manell-Geus Watersheds as a Habitat Focus Area because it is valuable as a natural resource to the coastal community of Merizo. As a Habitat Focus Area more resources are dedicated to the development and implementation of watershed management plans and conservation actions. To implement effective watershed management practices, it is important to a) have a better understanding of the available information about the watershed, b) have baseline information of the hydrologic conditions (ie., stream flow, stream level, turbidity, and precipitation over time) and, c) understand the behavior of the watershed. This study was funded by NOAA through the University of Guam Water and Environmental Research Institute (WERI) via the Guam Bureau of Statistics and Plans, Guam Coastal Management Program. The study determines baseline hydrologic conditions of the Geus Watershed, through field observations and hydrologic data collected from December 2013 to January 2015. Results show a strong correlation between stream level, turbidity, and rainfall within the watershed, suggesting the watershed is highly dynamic. The response of stream level and turbidity to rainfall in the Geus River was observed on time scales of hours. Field data collected also produced a stage discharge curve which increases the efficiency of future watershed management by providing an estimate of stream flow from a simple measure of water level. Supplemental analyses based on the results of soil samples and a GIS-based erosion model identified areas within the watershed with higher contributions to erosion potential. A synthesis of the information in this watershed study allows for recommendations of effective watershed management strategies and opens the way for evaluating progress within the Geus Watershed with continued monitoring.

Author(s):
Shahram Khosrowpanah
Mark A. Lander
Joseph Rouse
Bill Whitman